Biotinidase deficiency

Diagnosis and Testing

How do I get tested for biotinidase deficiency?

Most newborns born in the United States have newborn screening, and biotinidase deficiency is a recommended condition to be included in routine newborn screening. If you have questions about what conditions your state screens newborns for, and whether biotinidase deficiency is included, the Save Babies through Screening website provides links to state specific newborn screening information.

For diagnostic testing for biotinidase deficiency beyond the newborn period, you can discuss this testing with your primary care physician or geneticist. Biotinidase deficiency can be confirmed by either biochemical or molecular testing on blood.

For biochemical testing for biotinidase deficiency, the amount of biotinidase enzyme activity is measured in the blood. Individuals with biotinidase activity less than 10% of the normal average are diagnosed with profound biotinidase deficiency, while individuals with biotinidase activity 10-30% of the normal average are diagnosed with partial biotinidase deficiency. The diagnosis of profound or partial biotinidase deficiency can be made by biochemical (enzyme testing alone).

Molecular testing can also be used to diagnose biotinidase deficiency. The BTD gene is the name of the gene involved in biotinidase deficiency, and spelling errors in the BTD gene detected by sequencing of the gene are found in approximately 99% of individuals with biotinidase deficiency. BTD gene deletion/duplication can be done if gene sequencing does not identify two gene changes in affected individuals.

Genetic counselors may help you understand your testing options for biotinidase deficiency. The National Society of Genetic Counselors website includes a searchable "Find A Genetic Counselor" online directory to assist you in locating genetic counselors throughout the United States and Canada.

References
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More Diagnosis and Testing Content

Is there routine newborn testing for biotinidase deficiency?

Is there more than one test for biotinidase deficiency?

Who else in my family should I test for biotinidase deficiency?

Is there routine newborn testing for biotinidase deficiency?

Most newborns born in the United States have newborn screening, and biotinidase deficiency is a recommended condition to be included in routine newborn screening. If you have questions about what conditions your state screens newborns for, and whether biotinidase deficiency is included, the Save Babies through Screening website provides links to state specific newborn screening information.

If you are concerned that your newborn may have biotinidase deficiency and/or wonder whether newborn screening for biotinidase deficiency was performed on your baby, please talk with your child's pediatrician about your concerns and how to get more information about the possibility of testing or further evaluation.

References
Is there more than one test for biotinidase deficiency?

Biotinidase deficiency can be confirmed by either biochemical or molecular testing on blood.

For biochemical testing for biotinidase deficiency, the amount of biotinidase enzyme activity is measured in the blood. Individuals with biotinidase activity less than 10% of the normal average are diagnosed with profound biotinidase deficiency, while individuals with biotinidase activity 10-30% of the normal average are diagnosed with partial biotinidase deficiency. The diagnosis of profound or partial biotinidase deficiency can be made by biochemical (enzyme) testing alone.

Molecular testing can also be used to diagnose biotinidase deficiency. The BTD gene is the name of the gene involved in biotinidase deficiency, and spelling errors in the BTD gene detected by sequencing of the gene are found in approximately 99% of individuals with biotinidase deficiency. BTD gene deletion/duplication can be done if gene sequencing does not identify two gene changes in affected individuals.

Genetic counselors may help you understand your testing options for biotinidase deficiency. The National Society of Genetic Counselors website includes a searchable "Find A Genetic Counselor" online directory to assist you in locating genetic counselors throughout the United States and Canada.

References
Who else in my family should I test for biotinidase deficiency?

Once an individual has been diagnosed with biotinidase deficiency, evaluation of other family members is appropriate to determine if other members of a family are affected with or carriers of biotinidase deficiency. Since biotinidase deficiency is inherited in an autosomal recessive manner, the parents of an affected individual are each expected to be at a minimum carriers of biotinidase deficiency (or affected). If the parents are both carriers, then full siblings of an affected individual have a ¼ (25%) chance of being affected. Children of an affected individual will all be carriers of biotinidase deficiency and would be at risk of being affected or not depending upon the carrier status of their other parent. Unaffected siblings of an affected individual's parents (the affected individual's aunts and uncles) have a ½ (50%) chance of being a carrier of biotinidase deficiency.

Genetic counselors can assist a family in determining who in the family should be tested for biotinidase deficiency through the construction of a pedigree, or family tree. To locate a genetic counselor near you, you can consult the "Find A Genetic Counselor" searchable online directory on the National Society of Genetic Counselors website to locate genetic counselors throughout the United States and Canada.

References

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